1. Field of the Invention
The present invention relates to a method and system for extracting an edge of a distal radius used to predict an adult height of a child from an X-ray image.
2. Description of the Related Art
Recently, as concerns about children's growth increase, the development of a clinical method of predicting an adult height of a child and a treatment of increasing the adult height becomes main interests of children growth researches.
Particularly, the prediction of child's adult height is performed on the basis of bone age measurement of the child. Here, a bone age means the degree of physiological maturation of a child's bones that is different from a physical age of the child. Therefore, the bone age is not equal to the physical age, and the bone ages of persons in a state where bone maturation is finished are equal.
Therefore, the bone age is used as the degree of a child's growth remaining time. When the bone age is advanced than the physical age, a growth remaining time is short, and it is determined that the remaining growth of a child is short. Therefore, for a child of whose adult height is predicted to be short by the bone age measurement, growth treatment is needed to increase the adult height before the bone maturation is finished.
As representative methods for measuring bone age, there are a Greulich-Pyle (GP) method based on atlas and a Tanner-Whitehouse (TW) method of describing the degree of bone maturation as a score. Particularly, the TW is more objective and so widely applied. The TW method is improved as a TW2 method, and in 2000, a TW3 method is introduced.
In the TW3 method, by adding maturation scores of bone growth sites displayed in an X-ray image, RUS (radius, ulna, short bones) scores and carpal scores are obtained. In general, bone growth sites maturation grades are classified into A-I, that is, nine grades, and a maturation score corresponding to each bone maturation grade is provided.
In general, a clinical doctor determines a bone maturation grade from an X-ray image of a hand, converts the bone maturation grade into a maturation score, calculates RUS scores or carpal scores by adding bone maturation scores, and measures a bone age of a child, on the basis of the TW3 method.
Since the existing bone age measurement methods are performed by a subjective determination of the clinical doctor, errors may occur between clinical doctors, and even one doctor may provide different results in different time.
Therefore, an apparatus for computing a bone maturation grade objectively through a computer algorithm is required, and bone maturation grade computing apparatuses using several computer algorithms have been developed and applied.
However, most of the apparatuses associated with bone age measurement that have been clinically applied serve as tools for helping doctors to perform the TW3 bone age measurement easily using the acquired X-ray image and cannot compute the bone maturation grade by themselves. In addition, although a function of computing the bone maturation grade is included, doctors have to involve in the determination. In addition, although operations for computing bone maturation grades are automated, in some cases, accuracy of the result of the computation may not be guaranteed.
More specifically, the determination of a bone maturation grade is performed by classifying and assessing changes in shapes of an epiphysis and a metaphysis that form a bone growth site and the amount of fusion between the two bones. Therefore, for more accurate determination of the bone maturation grades, edges between the epiphysis and the metaphysis forming the bone growth site have to be accurately extracted.
However, in the existing method, extraction of the edge between the epiphysis and the metaphysis from the X-ray image is performed by applying various edge detection masks and a method of setting a gray level threshold. However, when the aforementioned method using the X-ray image is used to detect the edge, signal noises are mixed, so that there is a problem in that reliability of a result of the detection is decreased.
In addition, in order to reduce the effects of the signal noises from the X-ray image, some methods such as an Active Shape Model (ASM) or Snake are used to detect a bone edge line. In this case, a number of sample images have to be acquired in advance to manually segment bone edges by clinical doctors. In addition, according to methods of providing a curvature characteristic to the Snake, the performances of bone edge detection are changed. In addition, there is a problem in that a snake appropriate for various bone edges cannot be easily generated.
As described above, conventional methods of extracting an edge of the distal radius metaphysis which is an important factor to measure a bone age from an X-ray image have a problem in that accuracy of the result of the extraction is decreased and reliability of the bone age measurement is decreased.